Field of Invention
The present invention relates to a field of permanent magnetic materials, and more particularly to a method for manufacturing a high-performance NdFeB rare earth permanent magnetic device.
Description of Related Arts
NdFeB rare earth permanent magnetic materials are more and more widely used due to excellent magnetic properties thereof For example, the NdFeB rare earth permanent magnetic materials are widely used in medical nuclear magnetic resonance imaging, computer hard disk drivers, stereos, cell phones, etc. With the requirements of energy efficiency and low-carbon economy, the NdFeB rare earth permanent magnetic materials are also used in fields such as automobile parts, household appliances, energy conservation and control motors, hybrid cars and wind power.
In 1983, Japanese patents No. 1,622,492 and No. 2,137,496 disclosed NdFeB rare earth permanent magnetic materials invented by Japanese Sumitomo Metals Industries, Ltd., which disclose features, components and manufacturing methods of the NdFeB rare earth permanent magnetic materials, and confirm that a main phase is a Nd2Fe14B phase and a grain boundary phase comprises a rich Nd phase, a rich B phase and rare earth oxidants. NdFeB materials are widely used because of sufficient magnetic performance, and are called the king of permanent magnets. U.S. Pat. No. 5,645,651, authorized in 1997, further disclosed adding Co and the main phase having a square structure. The above patents are rigorous and therefore well protect the intellectual property. After purchasing Sumitomo Metal Industries, Ltd., Hitachi Metals, Ltd. filed a lawsuit against 29 enterprises comprising 3 Chinese NdFeB manufacturers to ITC in US with U.S. Pat. No. 6,461,565; U.S. Pat. No. 6,491,765; U.S. Pat. No. 6,537,385 and U.S. Pat. No. 6,527,874, wherein a patent family member of U.S. Pat. No. 6,461,565 is Chinese patent CN1195600C, which claims a temperature controlled at 5-30° C. during magnetic field pressing and a relative humidity of 40-65%. Although the above condition keeps safe and convenience during forming, an oxygen content is high, which wastes valuable rare earth resource and lowers performance A patent family member of U.S. Pat. No. 6,491,765 and U.S. Pat. No. 6,537,385 is Chinese patent CN1272809C, which claims a high-speed inert gas flow with a content of 0.02-5 during powdering with jet milling, for finely decrepitating alloys and removing at least a part of fine powder with a particle size less than 1.0 μm, so as to decrease a content of fine powder with the particle size less than 1.0 μm to lower than 10% of a total particle amount. Because the fine powder with the particle size less than 1.0 μm has a high rare earth content, a large surface area, is easiest to be oxidized, and is even easy to catch a fire, decrease thereof is conducive to process control and performance improvement. However, the rare earth is wasted. In addition, some fine powder with the particle size less than 1.0 μm is outputted through an outputting tube of a cyclone collector, which is controlled by a jet milling device and is difficult to be manually controlled. A patent family member of U.S. Pat. No. 6,527,874 is Chinese patent CN1182548C, which claims a strip casting alloy with Nb and Mo added, and a manufacturing method thereof. Strip casting alloy and manufacturing method thereof are firstly disclosed in U.S. Pat. No. 5,383,978, which greatly improves performance of NdFeB and has become a main manufacturing technology since 1997. Therefore, a lot of manpower and financial resources are used, resulting in rapid development of the technology. U.S. Pat. No. 5,690,752; CN97111284.3; CN1,671,869A; U.S. Pat. No. 5,908,513; U.S. Pat. No. 5,948,179; U.S. Pat. No. 5,963,774 and CN1,636,074A are all improvement of the technology.
With wide application of the NdFeB rare earth permanent magnets, rare earth is more and more rare. Especially, shortage of heavy rare earth element resource is significant, and price of the rare earth is continuously increasing. Therefore, after a lot of searching, double-alloy technology, metal infiltration technology, grain boundary improving or recombining technology, etc. appear. Chinese patent CN101521069B disclose a NdFeB manufacturing technology with heavy rare earth hydride nano-grain mixed, invented by Yue, ming et al. of Beijing University of Technology, wherein alloy flakes is firstly manufactured with strip casting technology, then powder is formed by hydrogen crushing and jet milling, the above power is mixed with heavy rare earth hydride nano-grains formed by physical vapor deposition technology, and then NdFeB magnet is manufactured through conventional processes such as magnetic field pressing and sintering. Although the Chinese patent discloses a method to enhance coercivity of magnet, research is not thorough enough and there is problem for mass production. Patents CN101,383,210B; CN101,364,465B; and CN101,325,109B disclose similar technologies, wherein performance is slightly improved, nano oxide is easy to absorb moisture, adsorbed water seriously affects product performance, and product consistency is poor.